Disabling Uncheck option in ion-select

Hi,

I am giving a dropdown using ion-select where user has a choice to select multiple options. While editing the form, i don’t want the user to deselect the options which he had already selected. Is there a way to disable these check boxes so that user only get option of selecting new values?

Cheers,
Ankit

Just to add, i want to disable items inside if they are already checked.